Week 1

Question 1

List the main fluid compartments of the human body, and compare their relative magnitude.

Answer 1

ICF(half of ECF), ECF(most), Plasma

Question 2

What 3 conditions are essential to enable the mechanism allowing blood plasma to control the composition of the interstitial fluid?

Answer 2

adequate blood flow, small diffusion distance and composition of blood must be controled

Question 3

What is the general process by which substances are transported between body cells and plasma?

Answer 3

diffusion between vessels and cells, transport in blood by convection

Question 4

Draw a diagram that shows the organs and pattern of blood flow in the pulmonary and systemic circulations.

Answer 4

pulmonary and systemic are separate circuits, they are in series while all components in the systemic circulation is in parallel

Question 5

Define cardiac output and state its approximate magnitude/range in a typical resting individual.

Answer 5

volume heart beats in a given time either from right or left ventricle; normally 5L/min

Question 6

List two important consequences of the parallel arrangement of organs in the systemic circulation.

Answer 6

all organs get the same quality blood and volume of blood to each organ can be controlled independently

Question 7

Explain why the kidneys must receive such a large fraction of the cardiac output.

Answer 7

kidneys condition the electrolyte composition of the whole blood system, receive a large amount total cardiac output

Question 8

Distinguish between organs that are “blood-conditioning” and those that are not, and list some examples of each type.

Answer 8

conditioning organs alter the composition of blood for other organs use (kidneys, lungs) others use only for their metabolic needs an are very sensitve to any reduction in flow

Question 9

Describe the relationship between flow, pressure, and resistance as it relates to a segment of a blood vessel. Write the equation formalizing that relationship.

Answer 9

flow equals pressure difference divided by the resistance over a distance (it is pressure gradient, not absolute pressure that determines flow (Q= ΔP/ R)

Question 10

List the variables that determine resistance to blood flow through a vessel, and write the mathematical formula relating them. Which variable normally plays the most influential role in varying resistance to blood flow?

Answer 10

diameter of the vessel, viscosity of blood, length of vessel R= (8Lη)/ (πr^4) Radius has the greatest impact on resistance

Question 11

Derive the Poiseuille equation and explain its application in the flow of blood

Answer 11

Q= ΔP (πr^4/8Lη) combines elements of flow and resistnace equations

Question 12

How does the pressure gradient between arteries and veins compare between different systemic organs, and what is the main determinant of differences in blood flow between them?

Answer 12

gradient between arteries and veins in different systems is similar, the main control of flow comes from the change in the radius of blood vessels/ ie. Changing the vascular resistance

Question 13

Write the equation that relates cardiac output to the two variables that determine it; list the units of all three quantities.

Answer 13

CO = SV x HR : CO [volume/min] = SV [volume/stroke] x HR [beats/minute],

Question 14

Trace the path of blood flow through the heart, naming all valves that determine the direction of flow.

Answer 14

right atrium, tricuspid valve, right ventricles,pulmonary valve, pulmonary circuit, left ventricle, mitral valve, left ventricle, aortic valve, and systemic circulation

Question 15

Explain what causes the opening and closing of cardiac valves.

Answer 15

valves open passively due to pressure differential between atria and ventricle

Question 16

Define the terms “systole” and “diastole.”

Answer 16

systeole (ventricular contraction) diastole (ventricular relaxation)

Question 17

Define the term “functional syncytium,” and explain how it relates to excitation of the heart.

Answer 17

the heart cells are electrically continuous for all purposes which is important for AP conduction and heart rhythm (cells connected by gap junctions)

Question 18

List the structural components of the heart’s specialized excitation and conduction system, and describe how each functions in the initiation and spread of action potentials through the heart.

Answer 18

SA- AV(slowest)- budle of His (only electrical connection between atria and ventricles), Purkinje fibers of the ventricles

Question 19

List five requirements for effective and efficient operation of the pumping action of the heart.

Answer 19

1. contractions at regular intervals and be synchronized, 2. valves must open fully (not stenotic), 3. valves must not leak (not insufficient), 4. muscle contractions must be forceful (not failing), 5. ventricles must fill adequately during diastole (stretchy compliance is required)

Question 20

Draw a figure that demonstrates Starling’s Law of the Heart, carefully labeling the axes; then, explain the significance of that relationship for the function of the heart.

Answer 20

As cardiac filling increases during diastole, the volume ejected during systole also increases, due to intrinsic property of the heart and primary regulator of cardiac output. Diastolic filling of ventricles determines stroke volume and therefore cardiac output.

Question 21

Describe the distribution of sympathetic and parasympathetic nerve endings on the heart, list the neurotransmitters and receptors involved, and then describe the effects of each system on the function of the heart.

Answer 21

sympathetic system has receptors on both atria and ventricles, through B1 receptors acted on by epi and norepi (heart rate, action potential, conduction velocity, force of contraction rate of contraction and relaxation); parasympathetic only has innervation on the atria to SA and AV nodes release Ach on muscarinic receptors (reduce conduction velocity and force)

Question 22

List the 5 general blood vessel types blood encounters in the systemic circulation as it passes from left ventricle to right atrium.

Answer 22

artery, arteriole, capillary, ventriole, vein

Question 23

Describe the histological features of the 5 general types of blood vessels, noting which features they have in common and which features distinguish them.

Answer 23

arteries (much elastic fibers) arterioles (much smooth muscle) capillaries (very thin lumen), veins and venules (very little muscle, valves very distensible but not elastic therfore hold a lot of blood). All vessels are lined with endothelium with anti-clotting properties

Question 24

Explain how the anatomy/histology of each systemic vessel type contributes to its main overall function.

Answer 24

Arteries: thick walled containing smooth muscle, elastin and collagen fibers (conduit vessels because the have low and unchanging resistance to flow), They have a lot of elasticity, they are considered the highways.

Arterioles: much thicker walls with more smooth muscle (a lot when considering their cross-sectional area) and less elastic material (resistance vessels)

Capillaries smallest vessels consisting of a single layer of endothelial cells and no smooth muscle (exchange vessels), given the example of the tea bag, with diabetes the excess glucose can gum up the basement membrane

Venous vessels have very thin walls in proportion to their diameters, their walls contain smooth muscle and thin walls are very distendible (holds a lot of blood but does not have the elasticity to “snap back” and diameters change in response to transmural distending pressure (capacitance vessels) and chances to venous volume influence cardiac filling and therefore cardiac pumping. (very important for cardiac output)

Question 25

Detail the 2 mechanisms that control the diameter of arterioles, and the one mechanism that controls the diameter of the veins

Answer 25

arterioles: sympathetic and paracrine regulation, veins: sympathetic innervation

Question 26

. Define the term hematocrit, and give an approximate value in a typical, healthy person.

Answer 26

the measure of formed solids (cells) in the blood, normally 40%

Question 27

List the 3 general types of formed elements in the blood, and state the general function of each.

Answer 27

RBC carry oxygen (most abundant), WBC immune function, Platelets clotting

Question 28

Explain the distinction between plasma and serum

Answer 28

Plasma has clotting elements, serum does not

Question 29

List the solutes found in the plasma component of blood, and note which are present in the highest concentration.

Answer 29

sodium, potassium, bicarbonate, chloride, in blood Sodium and chloride are most abundant

Question 30

Describe the composition of isotonic saline, and explain its clinical usefulness

Answer 30

saline is both sodium and chloride 150 mM

Question 31

List the 3 categories of plasma proteins, and describe the general function of each category

Answer 31

albumin (carrier) immunoglobulins (immune function) fibrinogen (clotting)

Question 32

List some of the organic nutrient and waste molecules dissolved in plasma.

Answer 32

amino acids, glucose, urea, creatinine and uric acid

Question 33

List some of the general characteristics of cardiac muscle cells.

Answer 33

demonstrate electrical conductance and reliable contractile and pumping characteristics

Question 34

List 3 ways that cardiac cell action potentials differ from skeletal muscle action potentials

Answer 34

contraction can be self generating, potentials can be directed from cell to cell, action potentials have long durations

Question 35

Review the following concepts of membrane biophysics: Ion gradients, equilibrium potentials, voltage-gated ion channel activation, ion-channel inactivation, resting membrane potentials, threshold potential, action potentials, absolutely refractory period, relative refractory period.

Answer 35

just do it.

Question 36

Draw a typical cardiac muscle cell action potential (fast-response cells), name the phases, and describe the ion-channel events that determine the shape.

Answer 36

Fast Response: Phase 4 (resting but changing membrane before AP, T type Ca active) Phase 0 (rising stroke due to fast Na channels opening and inactivating), Phase 1 (transient drop after peak) Phase 2 (AP plateau due to L tyep Ca channels) Phase 3 (down stroke due to K primarily, K is slow to respond)

Question 37

. Draw a typical cardiac muscle cell action potential (fast-response cells), name the phases, and describe the ion-channel events that determine the shape.

Answer 37

Fast Response: Phase 4 (resting but changing membrane before AP, T type Ca active) Phase 0 (rising stroke due to fast Na channels opening and inactivating), Phase 1 (transient drop after peak) Phase 2 (AP plateau due to L tyep Ca channels) Phase 3 (down stroke due to K primarily, K is slow to respond)

Question 38

37. Draw a typical cardiac node cell action potential (slow-response cell), name the phases, and describe the ion-channel events that determine the shape.

Answer 38

Slow response: Phase 4 (rising due to funny Na channels and contributing T type Ca) Phase 0-2 mostly due to Ca channels, L type) and Phase 3 (K+ conductance)

Question 39

38. Describe the structure and function of intercalated disks in cardiac cells.

Answer 39

to connect cardiac cells and conduct electrical currents; structures include hemdesmosomes and adherins for connection and conexins in gap junctions to create low resistance connections

Question 40

39. What three variables determine the variation in action potential conduction velocity in different regions of the heart?

Answer 40

Cell diameter (AV node small, Purkinje huge), intensity of depolarizing current (Na+> Ca2+ current), properties of membrane and gap junctions (second messengers, phosphorylation via autonomic receptors (ie. sympathetic

Question 41

40. Draw a graph demonstrating the spread of an action potential during a single beat of the heart, showing the shapes and relative timing of the action potential in the following cell types: SA node, Atrial muscle, AV node, Purkinje, ventricular muscle

Answer 41

action potential is staggered spacially as AP travels through heart; fast cells: earliest to depolarize take the “longest” to depolarize, and the last to depolarize are first to repolarize

Question 42

41. Explain in a general way what is measured by electrocardiography, and describe what cellular events are indicated by P, QRS, and T-waves.

Answer 42

EKG measures the electrical voltage between two points. P wave is atrial depolarization, QRS is ventricle depolarization, T is ventricle repolarization

Question 43

42. Define automaticity, and describe the cells that are the normal pacemaker of the heart, stating their intrinsic rate of activity.

Answer 43

Automaticity: contractions that occur due to spontaneous pacemaker activity SA node 100/min is the normal pacemaker of the heart

Question 44

43. Describe the cellular mechanisms by which parasympathetic and sympathetic neurons modulate automaticity of the heart.

Answer 44

by altering funny Na channel permeability

Acteylcholine released by parasympathetic nerves increase resting K+ permeability and decreases diastolic permeability to Na+ (funny currents) which drives the membrane potential more negative. Parasympathetic also decreases L-type Ca++ current and slow the upstroke, so conduction velocity is decreased in the cells of the atria (negative dromotropic effect- slows contraction speed)

Increasing sympathetic tone results in increases in heart rate while increasing parasympathetic tone decreases heart rate by altering the spontaneous depolarization of the pacemaker cells. This is done by norepi on B1 receptors which increases the funny Na current and Ca++ current (T type so cells reach potential faster). Sympathetic also increase L-type Ca++ current and speeds upstroke.

Question 45

44. Describe the dromotropic effect of sympathetic and parasympathetic neurons on cells of the AV node, and how that would be expected to alter cardiac function.

Answer 45

Dromotropic effect: conduction speed

Parasympathetic linked muscarinic receptors are linked to G inhibitory proteins to increase K+ permeability and decrease cAMP and reduce the inward going pacemaker current. Increased parasympathetic activity has a negative dromotropic effect.

Sympathetic nerves release norepi on B1 adrenergic receptors which are linked to stimulatory G proteins and increase the open state probability in Na+ current channel, increasing the rate of diastolic depolarization. Sympathetic increase AP velocity that has a positive dromotropic effect.
These effects are most apparent at the AV node and affect the PR interval.

Question 46

45. List the two sources of elevated cytosolic Ca2+ during contraction of cardiac muscle, state which causes the largest change, and explain how elevated Ca2+ leads to force generation.

Answer 46

A small change in intracellular Ca++ causes a large amount of Ca++ to be released from the sarcoplasmic reticulum. Ca++ increases the interaction between myosin and actin fibers
Variations in the amount of “trigger” Ca++ and the Ca++ release from the sarcoplasmic reticulum vary cardiac “contractility.”

Question 47

46. List the three mechanisms that remove Ca2+ from the cytosol of cardiac muscle cells after a contraction, and state the proportion of Ca2+ removed by each mechanism.

Answer 47

Active uptake into the Sarcoplasmic reticulum is 80%
Extrusion from the cell by Ca ATPase pumps 5%
Na/Ca++ exchanger 15% (powered by the sodium gradient to remove Ca++ from the cell)

Question 48

47. Explain how the cardiac glycoside, digitalis, increases contractile force in failing hearts.

Answer 48

Cardiac glycoside digitalis slows down the Na/K pump and thus reduces the sodium gradient. Therefore, increased Ca++ is sequestered in the SR and increases contractile force. (Na/K exchanger electrogenic effect also effects the AP plateau)

Question 49

48. Explain why cardiac muscle cells cannot undergo fused tetanic contractions like those occurring in skeletal muscle cells.

Answer 49

The contraction of cardiac muscle lasts as long as the action potential that caused it so there is no way to summate AP and contractile force. The cell cannot be activated fast enough to induce fused tetany.

Question 50

49. Differentiate between isotonic and isometric contractions of muscle cells.

Answer 50

Isotonic is constant tension and varying length, isometric is a muscle that does not change length although it might increase or decrease tension. Heart cells undergo isometric contraction before valves open and isotonic after valves open

Question 51

50. Draw a graph that shows the effect of increasing muscle length on resting muscle tension, active isometric muscle tension, and total muscle tension. Compare the length at which cardiac muscle normal operates, to the length on this graph where active tension is greatest (Lmax).

Answer 51

cardiac muscle operates normally way below the Lmax, therefore increasing the muscle length increases the tension developed

Question 52

51. Describe the contractile behavior that occurs when cardiac muscle contractile potential is greater than the load it contracts against.

Answer 52

. It will cause the muscle to contract isotonically and shorten. It will shorten until the muscles tension producing potential is decreased sufficiently by the length change to be equal to the load on the muscle

Question 53

52. Using a graph of muscle length vs muscle tension, differentiate between the contractile behavior of a muscle undergoing an isotonic contraction from a muscle undergoing an afterloaded contraction.

Answer 53

Preload stretches the ventricle then the ventricle isometrically contracts until meets the pressure of the valves (afterload) and isometricaly contracts until valves open and then isotonic contraction resumes

Question 54

53. State the distinguishing feature of an intervention that alters “contractility” of heart muscle.

Answer 54

Any intervention that that increases the peak isometric tension that a muscle can develop at a fixed length is said to increase the cardiac muscle contractility

Question 55

54. Draw a figure that demonstrates the effect of norepinephrine from sympathetic nerves on the contractility of cardiac muscle, differentiating between the effect on isometric and afterloaded contractions.

Answer 55

norepinephrine can affect the afterload in that it causes the cardiac muscle to shorten a greater distance than it would normally, it also increases the maximal isometric tension

Question 56

55. Detail the cellular mechanisms coupling norepinephrine binding to the positive inotropic and positive lusitropic effects on cardiac muscle cells.

Answer 56

G protins linked to a B1 receptor activates PKA to alter the action of calcium channels on the sarcoplasm and the sarcoplasmic reticulum; Inotropic: increases activity of Ltype Ca++ channels and affects ryanodine receptors which loads ERs (faster depolarization) Phosphorylation of phospholamban on the SR Ca ATPase increases the rate of calcium retrapping and decreases the action potential length—leads positive lusitrophic efffect

Question 57

56. Explain how changes in heart rate directly contribute to changes in cardiac muscle contractility.

Answer 57

inotropic effects on the heart during increased heart rate will lead to greater Ca++ in the cell and lusitropic effects will lead to faster relaxation, so overall a quicker contraction

Question 58

57. Describe three critical functional implications that arise from the fact that ventricular muscle cells are oriented circumferentially in the ventricular wall.

Answer 58

1. increase in ventricular volume increases ventricular circumference and thus the diastolic filling of the ventricle determines the preload
2. At any ventricular volume, an increase in the tension of individual cardiac muscles cells causes an increase intravetricular pressure
3. As ventricular volume decreases a lesser total force is required by the muscle cells in the ventricular walls to produce any give intraventricular pressure.

Question 59

58. Write the equation that expresses the law of Laplace, and explain how it applies to ventricular function.

Answer 59

T= Px r the relationship between total wall tension and internal pressure in a hollow vessel with circular containing walls depends on the intraventricular pressure and its internal radius. One application of this is that the muscle cells in the ventricular wall have an easier job producing internal pressure at the end of systole and significance in other pathological conditions. Dialated hearts (increased r) require more tension to generate a given pressure)

Question 60

59. Draw one comprehensive graph that shows the phases of a single cardiac cycle for the left side of the heart, relating the following cardiac variables over time: Lead 2 ECG, Muscle contraction, aortic pressure, left ventricular pressure, left atrial pressure, aortic and mitral valve opening/closing, heart sounds, left ventricular volume, and aortic blood flow. Be able to explain the causal and temporal relationships among all of these variables.

Answer 60

practice starting with the closing of the mitral valve. Include verticle lines that denote diastole and the 3 phases of systole

Question 61

60. Explain the major differences between the events described in the last question for the left side of the heart, and those same events as they occur in the right side of the heart.

Answer 61

Have same stroke volume, under same electrical control, right side is generally at a lower pressure. Pressures developed are considerably lower than that of the ventricles, the magnitude of the peak systolic pressure is much less in the atria (there is much less resistance in the pulmonary circuit

Question 62

61. List the 3 components of the jugular vein pulse, and explain the cause of each component.

Answer 62

A wave, atrial wave produces the first pressure peak (atrium contracts)
C wave follows shortly after due to the onset of ventricular systole and by an initial bulging of the tricuspid valve into the right atrium (ventricle contracts)
V wave, increased pressure as the central veins and right atrium fill behind a closed tricuspid valve with blood returning to the heart (atrium fills)

Question 63

62. Draw a graph showing the changing relationship between intraventricular volume and intraventricular pressure during a single cycle of the heart. Label the cardiac phases and note the points at which cardiac valves open and close.

Answer 63

isometric contraction of ventricle until overcomes after load volume, then isometric contraction to move blood out of heart. then isovolumetric relaxation and passive stretching during filling

Question 64

63. Define ventricular preload and ventricular afterload.

Answer 64

Ventricular preload is the ventricle loaded with blood and the pressure that puts on the ventricle and ventricular afterload is additional pressure that the aortic pressure adds against the contracting ventricle—important for opening of aortic valve (a range of values)

Question 65

64. Draw two superimposed ventricular pressure-volume loops that demonstrate the effect of preload on stroke volume.

Answer 65

greater preload results in greater stroke volume with no change in end diastolic volume

Question 66

65. Draw two superimposed ventricular pressure-volume loops that demonstrate the effect of afterload on stroke volume.

Answer 66

greater afterload results in less cardiac muscle shortening, after resulting in reduced stroke volume and increased end-systolic volume

Question 67

66. Draw two superimposed ventricular pressure-volume loops that demonstrate the effect of changes in cardiac muscle contractility on stroke volume.

Answer 67

contractility increases stroke volume, greater end diastolic volume can stretch cardiomyocytes and increase contractility along with NE or Epi

Question 68

67. Summarize the effects of cardiac parasympathetic nerve activity level, cardiac sympathetic nerve activity level, arterial pressure, and filling pressure on 1)heart rate, 2) stroke volume, and 3) cardiac output.

Answer 68

Ach on muscarinic receptors decreases peak isometric tension and amount of shortening at any length, at a given preload, decreases rate of pressure development and SV, emptying of heart to a larger end systolic volume

Question 69

68. Draw and explain a graph showing the effect of sympathetic nerve activity level on the relationship between cardiac filling pressure and cardiac output.

Answer 69

increasing preload leads to more shortening cardiomyocytes

Question 70

69. Define angina pectoris, and describe its direct and indirect causes.

Answer 70

Severe chest pain or discomfort due to a mismatch in the metabolic requirements of the heart and what is supplied by the coronary arteries, due to cardiac ischemia